The invention relates generally to methods for processing polyolefin textiles, and more particularly to such methods used to increase water vapor transfer in polyolefin textiles that are subject to user perspiration and were originally hydrophobic but after several use cycles of wearing, soiling and washing became hydrophilic.
Polyolefins used for clothing often suffer the disadvantage of deteriorating over time and use from their original ability to direct water vapor away from the skin of a user. Some characterize the polyolefin fabric after some use as having lost its original ability to xe2x80x9cbreathexe2x80x9d, making them feel hot and sticky. Attempts to restore the originally hydrophobic polyolefin fabric back to its original hydrophobic property have failed despite many subsequent detergent washings.
The problem of perspiring in polyolefin fabrics can become serious for a person in a sub-freezing environment over time. The person may suffer cold injury or hypothermia if moisture or ice accumulates in his protective clothing against his skin. Transpiration, perspiring and exposure to water outdoors in winter can all contribute to this problem. Because water conducts many times more heat away from the body than a still air layer of an equal thickness does, wet polyolefin fabrics against the skin in freezing cold can present a serious threat to life, limb, fingers and toes through frost bite, hypothermia or death. Even uncomfortable wet socks from perspiring in winter boots can become a problem.
Perspiring in polyolefin fabrics can also be uncomfortable. Jogging in a windbreaker on a comfortable day or playing tennis on a hot day in wet nylon or cotton socks where water liquid and vapor is trapped or restricted against one""s skin feels unpleasant and breeds fungus.
There have been numerous attempts over many years to improve man made fabrics including polyolefin fabrics by transferring the water perspiration through the polyolefin fabrics to the outside ambient air. Some may recall the polyester leisure suits of the 1960""s that touted the promise of xe2x80x9chigh tech fabrics that breathexe2x80x9d but delivered something else. There remains a long felt need for improving the comfort of a person perspiring in a polyolefin garment by improving the water vapor transfer efficiency in polyolefin fabrics over time and use.
A method for improving the water vapor transfer efficiency of polyolefin fabrics which were originally hydrophobic but after several use cycles of wearing, soiling and washing become less hydrophobic and even hydrophilic has been discovered. Instead of a normally deteriorating or diminishing contact angle with water over time with resultant reduced hydrophobicity, that polyolefin process of the present invention maintains its original hydrophobic property of having a contact angle with water of at least 90 degrees over time and use. The processed hydrophobic polyolefin provides the advantage of remaining hydrophobic over time and through repeated use cycles of wearing, soiling and washing. The open pores of a processed hydrophobic polyolefin can do a better job of directing water vapor away from the skin than the semi-occluded pores of an unprocessed polyolefin that had become less hydrophobic or even hydrophilic over time and use.
The resulting product and benefit of the invention process is an enhanced polyolefin fabric that works better than an unprocessed polyolefin fabric in applications such as clothing for people in sub-freezing environments to help them feel drier and warmer. Also the processed polyolefin fabric works better than an unprocessed polyolefin fabric over time and use in a hot climate by helping the perspiring user to feel cooler and drier. For example, a bilayered configuration of a processed polyolefin sock worn by a tennis player on a hot day feels more comfortable because the condensation and evaporation takes place away from the skin causing the person to experience dryness.
The method for maintaining the hydrophobicity of a polyolefin textile material comprises the steps of providing a solution having a pH level between 3.5 and 5.9; subjecting the hydrophobic polyolefin textile material to the solution; and after the subjecting step, drying the polyolefin textile material so that the hydrophobic polyolefin textile material maintains hydrophobicity with a contact angle with water of at least 90 degrees through repeated use cycles of wearing, soiling and washing. The resulting textile material is thus more permanently hydrophobic with a contact angle with water of at least 90 degrees.
In one embodiment of the invention the polyolefin textile material is a monolayer configuration. In another embodiment of the invention the polyolefin textile material is a bilayer configuration. The polyolefin textile material may comprise a bulk continuous filament yam.
The step of subjecting the hydrophobic polyolefin textile material to the solution is continued for at least about ten minutes. The solution is a laundry sour such as a citric wash. The solution comprises hot water at a temperature of about 120xc2x0 F. The step of subjecting includes rinsing with cold water and maintaining a pH between 3.5 and 5.9 pH for at least ten minutes.
The step of drying comprises placing the polyolefin textile material into a spin extractor for at least five minutes; and subsequent to the step of placing the polyolefin textile material into a spin extractor, drying the textile material in a tumble dryer at 150xc2x0 F. for at least 20 minutes.
As a result of subjecting the polyolefin fibers to a 3.5 to 5.9 pH solution, the processed surface of pores or interstices within the fiber form a contact angle with water of greater than 90xc2x0, and thereby retain the hydrophobic property of the polyolefin fabric through repeated use cycles of wearing, soiling and washing. Consequently, water vapor transfer is improved in the polyolefin fabric because the polyolefin fibers do not saturate or wick and thus retain less liquid perspiration. Because these processed fibers swell less from the perspiration liquid, the cavity size of the fabric pores remain open and will retain a greater volume of air space for facilitating more diffusion of perspiration vapor from the skin, through the fabric to the outside ambient air.